From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2132C48BE5 for ; Tue, 22 Jun 2021 12:33:33 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6261360FEA for ; Tue, 22 Jun 2021 12:33:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6261360FEA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33006 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lvfau-0006d9-Am for qemu-devel@archiver.kernel.org; Tue, 22 Jun 2021 08:33:32 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33378) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lvfZ2-0004YT-UZ; Tue, 22 Jun 2021 08:31:37 -0400 Received: from szxga08-in.huawei.com ([45.249.212.255]:2243) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lvfYw-0002qt-Hu; Tue, 22 Jun 2021 08:31:36 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4G8Qc65DCHz1BQQB; Tue, 22 Jun 2021 20:26:14 +0800 (CST) Received: from dggpemm500023.china.huawei.com (7.185.36.83) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Tue, 22 Jun 2021 20:31:23 +0800 Received: from [10.174.187.128] (10.174.187.128) by dggpemm500023.china.huawei.com (7.185.36.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Tue, 22 Jun 2021 20:31:22 +0800 Subject: Re: [RFC PATCH v4 0/7] hw/arm/virt: Introduce cpu topology support To: Andrew Jones , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= References: <20210622093413.13360-1-wangyanan55@huawei.com> <20210622114634.crjqusw6x6oj4j6v@gator> From: "wangyanan (Y)" Message-ID: Date: Tue, 22 Jun 2021 20:31:22 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20210622114634.crjqusw6x6oj4j6v@gator> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.174.187.128] X-ClientProxiedBy: dggeme707-chm.china.huawei.com (10.1.199.103) To dggpemm500023.china.huawei.com (7.185.36.83) X-CFilter-Loop: Reflected Received-SPF: pass client-ip=45.249.212.255; envelope-from=wangyanan55@huawei.com; helo=szxga08-in.huawei.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Barry Song , Peter Maydell , "Michael S . Tsirkin" , wanghaibin.wang@huawei.com, qemu-devel@nongnu.org, yangyicong@huawei.com, Shannon Zhao , qemu-arm@nongnu.org, Alistair Francis , prime.zeng@hisilicon.com, Paolo Bonzini , yuzenghui@huawei.com, Igor Mammedov , zhukeqian1@huawei.com, David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2021/6/22 19:46, Andrew Jones wrote: > On Tue, Jun 22, 2021 at 11:18:09AM +0100, Daniel P. Berrangé wrote: >> On Tue, Jun 22, 2021 at 05:34:06PM +0800, Yanan Wang wrote: >>> Hi, >>> >>> This is v4 of the series [1] that I posted to introduce support for >>> generating cpu topology descriptions to guest. Comments are welcome! >>> >>> Description: >>> Once the view of an accurate virtual cpu topology is provided to guest, >>> with a well-designed vCPU pinning to the pCPU we may get a huge benefit, >>> e.g., the scheduling performance improvement. See Dario Faggioli's >>> research and the related performance tests in [2] for reference. So here >>> we go, this patch series introduces cpu topology support for ARM platform. >>> >>> In this series, instead of quietly enforcing the support for the latest >>> machine type, a new parameter "expose=on|off" in -smp command line is >>> introduced to leave QEMU users a choice to decide whether to enable the >>> feature or not. This will allow the feature to work on different machine >>> types and also ideally compat with already in-use -smp command lines. >>> Also we make much stricter requirement for the topology configuration >>> with "expose=on". >> Seeing this 'expose=on' parameter feels to me like we're adding a >> "make-it-work=yes" parameter. IMHO this is just something that should >> be done by default for the current machine type version and beyond. >> I don't see the need for a parameter to turnthis on, especially since >> it is being made architecture specific. >> > I agree. > > Yanan, we never discussed an "expose" parameter in the previous versions > of this series. We discussed a "strict" parameter though, which would > allow existing command lines to "work" using assumptions of what the user > meant and strict=on users to get what they mean or an error saying that > they asked for something that won't work or would require unreasonable > assumptions. Why was this changed to an "expose" parameter? Yes, we indeed discuss a new "strict" parameter but not a "expose" in v2 [1] of this series. [1] https://patchwork.kernel.org/project/qemu-devel/patch/20210413080745.33004-6-wangyanan55@huawei.com/ And in the discussion, we hoped things would work like below with "strict" parameter: Users who want to describe cpu topology should provide cmdline like -smp strict=on,cpus=4,sockets=2,cores=2,threads=1 and in this case we require an more accurate -smp configuration and then generate the cpu topology description through ACPI/DT. While without a strict description, no cpu topology description would be generated, so they get nothing through ACPI/DT. It seems to me that the "strict" parameter actually serves as a knob to turn on/off the exposure of topology, and this is the reason I changed the name. Thanks, Yanan . > Thanks, > drew > > .